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Multi-Scale Remote Sensed Imagery for Mineral Exploration

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A special issue of Remote Sensing (ISSN 2072-4292). This special issue belongs to the section "Remote Sensing in Geology, Geomorphology and Hydrology".

Deadline for manuscript submissions: closed (1 December 2023) | Viewed by 10731

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Special Issue Editors

Prof. Dr. Zhengyong Ren

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Guest Editor

School of Geosciences and Info-Physics, Central South University, Changsha 410083, China
Interests: geo-electromagnetic induction methods for mineral exploration; joint inversions for minerals
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Jianhui Li

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Wutanlou Building, West District, China University of Geosciences (Wuhan), Wuhan 430074, China
Interests: electromagnetic induction method; forward modeling and inversion; data processing

Prof. Dr. Hongzhu Cai

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Guest Editor

Foundation Committee Building, West District, China University of Geosciences (Wuhan), Wuhan 430074, China
Interests: geophysical electromagnetic method; gravity and magnetic

Dr. Xushan Lu

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Guest Editor

Department of Earth Sciences, Memorial University of Newfoundland, St. John’s, NL A1B 3X5, Canada
Interests: geophysical electromagnetic method

Prof. Dr. Jingtian Tang

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Guest Editor

School of Geoscience and Info-Physics, Central South University, Changsha 410083, China
Interests: theory of geo-electromagnetic methods; forward and inversion

Special Issue Information

Dear Colleagues,

Minerals are important resources for the survival of human society and economic development of the world. With the rapid development of emerging industries, such as new-generation information technology and high-end equipment manufacturing, the demand for minerals remains high, especially for a variety of strategic minerals such as rare earth, cobalt, and lithium. Addition, the projects of achieving carbon peaking and carbon neutrality are inseparable from mineral resources, as increased use of new energy sources, especially solar, wind and nuclear power, will increase the demand for the associated mineral resources. Therefore, it is critical to explore more minerals and to increase the reserves of minerals resources.

The aim of the Special Issue is to present new theories, methods and techniques which are used to remotely sense or explore minerals resources. As key remote sensing techniques, geophysical methods, such as electromagnetic induction, the gravity and magnetic, and seismic methods, can efficiently locate the geometry of underground minerals. Using advanced data interpreting techniques and the help of laboratory experiments on rock samples, the geophysical method even has the ability to identify mineral composition. Data acquired by sensors installed on land, in boreholes, on helicopters and ships, on airborne devices and even on satellites have the chance to detect multiscale minerals resources. During the past ten years, along with the rapid evolution of acquisition instrument and data interpretation techniques, there have been significant developments in geophysical exploration methods. Therefore, it is indispensable to present and share these new developments.

As geophysical methods are indispensable techniques to the remote exploration of minerals resources, this topic is suitable to the scope of Remote Sensing.

The article can cover geophysical electromagnetic induction methods, gravity and magnetic, and geophysical seismic method. Works on laboratory experiments on rock samples, geological metallogenic mechanism of minerals resources, and even remote sensing methods are also welcome.

The types of articles submitted can be either reviewer articles or regular articles.

Prof. Dr. Zhengyong Ren
Prof. Dr. Jianhui Li
Prof. Dr. Hongzhu Cai
Dr. Xushan Lu
Prof. Dr. Jingtian Tang
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Remote Sensing is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

electromagnetic induction method
gravity
magnetic
seismic method

Published Papers (9 papers)

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Research

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19 pages, 5894 KiB

Open AccessArticle

Noise Attenuation for CSEM Data via Deep Residual Denoising Convolutional Neural Network and Shift-Invariant Sparse Coding

by Xin Wang, Ximin Bai, Guang Li, Liwei Sun, Hailong Ye and Tao Tong

Remote Sens. 2023, 15(18), 4456; https://doi.org/10.3390/rs15184456 - 10 Sep 2023

Cited by 3 | Viewed by 1065

Abstract

To overcome the interference of noise on the exploration effectiveness of the controlled-source electromagnetic method (CSEM), we improved the deep learning algorithm by combining the denoising convolutional neural network (DnCNN) with the residual network (ResNet), and propose a method based on the residual denoising convolutional neural network (ResDnCNN) and shift-invariant sparse coding (SISC) for denoising CSEM data. Firstly, a sample library was constructed by adding simulated noises of different types and amplitudes to high-quality CSEM data collected. Then, the sample library was used for model training in the ResDnCNN, resulting in a network model specifically designed for denoising CSEM data. Subsequently, the trained model was employed to denoise the measured data, generating preliminary denoised data. Finally, the preliminary denoised data was processed using SISC to obtain the final denoised high-quality data. Comparative experiments with the ResNet, DnCNN, U-Net, and long short-term memory (LSTM) networks demonstrated the significant advantages of our proposed method. It effectively removed strong noise such as Gaussian, impulse, and square wave, resulting in an improvement of the signal-to-noise ratio by nearly 20 dB. Testing on CSEM data from Sichuan Province, China, showed that the apparent resistivity curves plotted using our method were smoother and more credible. Full article

(This article belongs to the Special Issue Multi-Scale Remote Sensed Imagery for Mineral Exploration)

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18 pages, 3452 KiB

Open AccessArticle

Appraisal of the Magnetotelluric and Magnetovariational Transfer Functions’ Selection in a 3-D Inversion

by Hui Yu, Bin Tang, Juzhi Deng, Hui Chen, Wenwu Tang, Xiao Chen and Cong Zhou

Remote Sens. 2023, 15(13), 3416; https://doi.org/10.3390/rs15133416 - 5 Jul 2023

Viewed by 1139

Abstract

Magnetotelluric (MT) and magnetovariational (MV) sounding are two principal geophysical methods used to determine the electrical structure of the earth using natural electromagnetic signals. The complex relationship between the alternating electromagnetic fields can be defined by transfer functions, and their proper selection is crucial in a 3-D inversion. A synthetic case was studied to assess the capacity of these transfer functions to recover the electrical resistivity distribution of the subsurface and to evaluate the advantages and disadvantages of using the tipper vector W to complement the impedance tensor Z and the phase tensor Φ. The analysis started with two sensitivity tests to appraise the sensitivity of each type of transfer function, which is calculated for an oblique conductor model, showing that the resistivity perturbation of the same model will produce distinct perturbations to different transfer functions; the transfer function sensitivity is significantly different. A 3-D inversion utilizing the quasi-Newton method based on the L-BFGS formula was performed to invert different transfer functions and their combinations, along with quantifying their accuracy. The synthetic case study illustrates that a 3-D inversion of either the Z or Φ responses presents a superior ability to recover the subsurface electrical resistivity; joint inversions of the Z or Φ responses with the W responses possess superior imaging of the horizontal continuity of the conductive block. The appraisal of the 3-D inversion results of different transfer functions can facilitate assessing the advantages of different transfer functions and acquiring a more reasonable interpretation. Full article

(This article belongs to the Special Issue Multi-Scale Remote Sensed Imagery for Mineral Exploration)

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24 pages, 11455 KiB

Open AccessArticle

Simulation of Seismoelectric Waves Using Time-Domain Finite-Element Method in 2D PSVTM Mode

by Jun Li, Changchun Yin, Yunhe Liu, Luyuan Wang and Xinpeng Ma

Remote Sens. 2023, 15(13), 3321; https://doi.org/10.3390/rs15133321 - 29 Jun 2023

Cited by 1 | Viewed by 988

Abstract

The study of the numerical simulation of seismoelectric effects is very helpful for understanding the theory and mechanism of seismoelectric activities. Quasi-static approximation is widely used in the numerical simulation of seismoelectric fields. However, numerical errors occur when the model domain is not within the near-field area of EM waves or the medium is of high salinity. To solve this problem, we propose a time-domain finite-element algorithm (FETD) based on the full-wave electromagnetic (EM) equation to simulate seismoelectric waves in 2D PSVTM mode. By decomposing the electrokinetic coupling equations into two independent ones, we can solve the seismoelectric waves separately. In our implementation, we focus our attention on the solution of EM waves based on vector–scalar potentials, while using the open-source code SPECFEM2D to explicitly solve Biot’s equations and obtain the relative fluid–solid displacement, which is taken as the source for the complete Maxwell’s equations. In the solution of EM wave fields, we use an unconditionally stable implicit method for time discretization. Computation efficiency can be improved by combining explicit and implicit recursions. After conducting the mathematical formulation, we first validate our method by comparing its results with the analytic solutions for a half-space and a two-layer model, as well as with a quasi-static approximation method. Moreover, we run numerical simulations and wavefield analyses on an elliptical hydrocarbon reservoir, and reveal that the interface responses are promising for the identification of underground interfaces and hydrocarbon reservoir exploration. Full article

(This article belongs to the Special Issue Multi-Scale Remote Sensed Imagery for Mineral Exploration)

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18 pages, 6752 KiB

Open AccessArticle

Inverse Scattering Series Internal Multiple Attenuation in the Common-Midpoint Domain

by Jian Sun, Kristopher A. Innanen, Zhan Niu and Matthew V. Eaid

Remote Sens. 2023, 15(12), 3002; https://doi.org/10.3390/rs15123002 - 8 Jun 2023

Viewed by 848

Abstract

Internal multiple prediction remains a high-priority problem in seismic data processing, such as subsurface imaging and quantitative amplitude analysis and inversion, particularly in the common-midpoint (CMP) gathers, which contain multicoverage reflection information of the subsurface. Internal multiples, generated by unknown reflectors in complex environments, can be reconstructed with certain combinations of seismic reflection events using the inverse scattering series internal multiple prediction algorithm, which is usually applied to shot records in source–receiver coordinates. The computational overhead is one of the major challenges limiting the strength of the multidimensional implementation of the prediction algorithm, even in the coupled plane-wave domain. In this paper, we first comprehensively review the plane-wave domain inverse scattering series internal multiple prediction algorithm, and we propose a new scheme of achieving 2D multiple attenuation using a 1.5D prediction algorithm in the CMP domain, which significantly reduces the computational burden. Moreover, we quantify the difference in behavior of the 1.5D prediction algorithm for the shot/receiver and the CMP gathers on tilted strata. Numerical analysis of prediction errors shows that the 1.5D algorithm is more capable of handling dipping generators in the CMP domain than in the shot/receiver gathers, and it is able to predict the accredited traveltimes of internal multiples caused by dipping reflectors with small inclinations. For more complex cases with large inclination, using the 1.5D prediction algorithm, internal multiple predictions fail both in the CMP domain and in the shot/receiver gathers, which require the full 2D prediction algorithm. To attenuate internal multiples in the CMP gathers generated by large-dipping strata, a modified version is proposed based on the full 2D plane-wave domain internal multiple prediction algorithm. The results show that the traveltimes of internal multiples caused by dipping generators seen in the simple benchmark example are correctly predicted in the CMP domain using the modified 2D prediction algorithm. Full article

(This article belongs to the Special Issue Multi-Scale Remote Sensed Imagery for Mineral Exploration)

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17 pages, 4834 KiB

Open AccessArticle

3D Airborne EM Forward Modeling Based on Finite-Element Method with Goal-Oriented Adaptive Octree Mesh

by Xue Han, Jianfu Ni, Changchun Yin, Bo Zhang, Xin Huang, Jiao Zhu, Yunhe Liu, Xiuyan Ren and Yang Su

Remote Sens. 2023, 15(11), 2816; https://doi.org/10.3390/rs15112816 - 29 May 2023

Cited by 2 | Viewed by 1074

Abstract

The finite-element (FE) method for three-dimensional (3D) airborne electromagnetic (AEM) modeling can flexibly simulate complex geological structures at high accuracy. However, it has low efficiency and high computational requirements. To solve these problems, one needs to generate meshes more reasonably. In view of this, we develop an adaptive octree meshing scheme for frequency-domain AEM modeling. The octree meshes have the characteristics of regularity and flexibility, while the adaptive algorithm can effectively refine the mesh locally. In our adaptive mesh generation, the posterior errors and weighted coefficients are used to construct the final weighted posterior errors. We verify the accuracy of our method by comparing its results with semi-analytical solutions for a half-space model. Furthermore, we use the spectral-element (SE) method and our method to calculate EM responses for an abnormal block model and compare their computational costs. The results show that our adaptive scheme has obviously technical advantages over SE method for AEM modeling with multiple frequencies and multiple survey stations. Finally, we calculate a model with complex geological structures to verify the feasibility of our algorithm in complex geological circumstances. Full article

(This article belongs to the Special Issue Multi-Scale Remote Sensed Imagery for Mineral Exploration)

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19 pages, 16465 KiB

Open AccessArticle

Three-Dimensional Dual-Mesh Inversions for Sparse Surface-to-Borehole TEM Data

by Luyuan Wang, Yunhe Liu, Changchun Yin, Yang Su, Xiuyan Ren and Bo Zhang

Remote Sens. 2023, 15(7), 1845; https://doi.org/10.3390/rs15071845 - 30 Mar 2023

Cited by 1 | Viewed by 1309

Abstract

The surface-to-borehole transient electromagnetic (SBTEM) method can provide images at higher resolution for deep earth because its receivers are close to targets. However, as usually the boreholes distribute sparsely, the limited EM data can result in an “equivalent trap” in SBTEM inversions, i.e., the data are well-fitted, but the model is not properly recovered. To overcome this non-unique problem, we propose a dual-mesh three-dimensional (3D) SBTEM inversion scheme. We first use a coarse mesh to obtain a rough resistivity distribution near the borehole, and then we map the coarse mesh attribute into a fine one and capture details from the fine mesh inversion. We test our method on both synthetic data and survey data acquired in Daye, Hubei Province, China. Numerical experiments show that our dual-mesh inversion strategy can better recover the location and resistivity of targets. Full article

(This article belongs to the Special Issue Multi-Scale Remote Sensed Imagery for Mineral Exploration)

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17 pages, 6881 KiB

Open AccessArticle

Metallogenic Prediction of Magnetite in the Pandian Area at the Northwest Margin of Luxi Uplift, China: Constraints of Wide-Field Electromagnetic Data

by Jianxin Liu, Keke Zhou, Hongda Liu, Rongwen Guo, Yunqi Zhu, Zihao Zhang and Rong Liu

Remote Sens. 2023, 15(5), 1217; https://doi.org/10.3390/rs15051217 - 22 Feb 2023

Cited by 3 | Viewed by 1314

Abstract

The Pandian deposit is a newly discovered contact metasomatic skarn magnetite deposit found in the Cainozoic super-thick overburden on the northwest margin of Luxi Uplift (LXU). Presently, the horizontal scale of the deposit delineated by the potential field (gravity and magnetic method) has shown giant potential for ore deposits, and mapping the ore-controlling structures in the vertical scale becomes a primary task for metallogenic prediction. In our study, the wide-field electromagnetic method (WFEM), with a strong anti-noise ability in recording electromagnetic signals on the surface at multiple frequencies, is applied to characterize the deep conductivity distribution of the Pandian area. Based on the inversion results from two parallel WFEM profiles, which consist of 105 sites and previous geological and geophysical results, the 2D geoelectric models are established. The low-resistivity regions (with a typical range of 25~32 Ω·m) in the electrical models are proven to be ore bodies of Pandian deposit, which are developed along the contact zone between Yanshanian intrusive rocks and Paleozoic Ordovician strata. The scattered bodies (typically >32 Ω·m) in Ordovician limestone strata are probably caused by intrusive diorite pluton closely related to magnetite mineralization. Due to contact metasomatism, bedded limestone near magnetite was metamorphosed into marble and accompanied by low-resistivity skarn alteration, with resistivity much different from its high-resistivity protolith. The inverted geoelectrical models visually reflect the spatial distribution features of intrusive rocks and lithologic alteration/fracture zones. Full article

(This article belongs to the Special Issue Multi-Scale Remote Sensed Imagery for Mineral Exploration)

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19 pages, 59549 KiB

Open AccessTechnical Note

Near-Surface Geophysical Characterization of a Marble Deposit to Promote a Sustainable Small-Scale Mining

by Nathália de Souza Penna, Jorge Luís Porsani, Rodrigo Corra Rangel, Victor Hugo Hott Costa, Nicolas Correa de Oliveira, Marcelo Cesar Stangari and Conrado de Carvalho Braz de Faria Sousa

Remote Sens. 2024, 16(7), 1147; https://doi.org/10.3390/rs16071147 - 26 Mar 2024

Viewed by 502

Abstract

Small-scale mining (SSM) is responsible for almost all the production of non-metallic minerals in the world and represents around 80% of the mining in Brazil. The lack of direct geological information increases the level of uncertainty associated with the exploratory process, compromises mine planning, limits mineral extraction, and contributes to maximizing environmental issues. In this research, near-surface geophysical methods, including Electrical Resistivity, Capacitive Resistivity, Ground Penetrating Radar (GPR), and Transient Electromagnetic (TEM), were applied to characterize a marble deposit in an SSM located in the Campos do Jordão region, São Paulo state, southeast Brazil. The geophysical methods used provide indirect information about the subsurface geology based on the contrast in electrical and electromagnetic properties. Resistivity results show the efficiency of locating marble deposits, as well as fracture zones. GPR profiles allowed for the investigation of the structural heterogeneities in the subsurface. Geophysical data and lithological information from drill holes were integrated into Micromine software and guided the development of a geological model and a conceptual pit model. The information inferred from the pit modeling allowed us to analyze the potential of the deposit and should be used to assist in developing sustainable mining planning. The results of this work demonstrate that the investment in geophysical research can support the modernization of an SSM and contribute to more sustainable and productive mining. Full article

(This article belongs to the Special Issue Multi-Scale Remote Sensed Imagery for Mineral Exploration)

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15 pages, 8883 KiB

Open AccessTechnical Note

Q-Compensated Gaussian Beam Migration under the Condition of Irregular Surface

by Jianguang Han, Qingtian Lü, Bingluo Gu and Jiayong Yan

Remote Sens. 2023, 15(15), 3761; https://doi.org/10.3390/rs15153761 - 28 Jul 2023

Viewed by 592

Abstract

The viscosity of actual underground media can cause amplitude attenuation and phase distortion of seismic waves. When seismic images are processed assuming elastic media, the imaging accuracy for the deep reflective layer is often reduced. If this attenuation effect is compensated, the imaging quality of the seismic data can be significantly improved. Q-compensated Gaussian beam migration (Q-GBM) is an effective seismic imaging method for viscous media, and it has the advantages of both wave equation and ray-based Q-compensated imaging methods. This study develops a Q-GBM method in visco-acoustic media with an irregular surface. Initially, the basic principles of Gaussian beam in visco-acoustic media are introduced. Then, by correcting the complex-value time of the Gaussian beam in visco-acoustic media, energy compensation and phase correction are carried out for the forward continuation wavefield at the seismic source of the irregular surface and the reverse continuation wavefield at the beam center, which effectively compensates the absorption and attenuation effects of visco-acoustic media on the seismic wavefield. Further, a Q-GBM method under the irregular surface is proposed using cross-correlation imaging conditions. Through migration tests for three numerical models of visco-acoustic media with irregular surfaces, it is verified that our method is an effective depth domain imaging technique for seismic data in visco-acoustic media under the condition of irregular surfaces. Full article

(This article belongs to the Special Issue Multi-Scale Remote Sensed Imagery for Mineral Exploration)

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